The Ichthys Field: challenges of geological modelling for the field development

Abstract

Preparation for the Ichthys Field development has been underway since the final investment decision was made in January 2012. The Ichthys Field comprises two reservoirs: the Brewster Member of the Early Cretaceous Upper Vulcan Formation; and the Jurassic Plover Formation. The development will be phased in separate drilling campaigns, commencing with the core area of the Brewster Member reservoir. This reservoir has geological challenges, including: complexity of porosity and permeability distribution in the generally homogeneous sandstone reservoir; and, high gas saturation immediately above and below the free water level. The Ichthys Subsurface team has built geological models of the Brewster Member reservoir. The following methodologies were adopted into the geological models: broad-band seismic inversion data to distribute reservoir porosity away from well control; K Nearest Neighbour methodology to predict permeability from logs utilising core measurements; Cathode-luminescence analysis to understand permeability reduction within the field; imbibition Sw height functions to model high gas saturation immediately above and below the free water level; and, scenario-based geological uncertainty modelling. A series of geological models were utilised to optimise development well locations and to ensure sufficient production from the reservoir.